Display screen or portion thereof having a graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof having a graphical user interface; and,

FIG. 2 is a front view of a second embodiment of a display screen or portion thereof having a graphical user interface.

The dashed broken lines depict portions of the display screen or portion thereof having a graphical user interface and/or the display screen itself and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof having a graphical user interface, as shown and described. 